VLC is telling you the truth - it looks to me (without actually seeing the file) that your MP4 file is a MPEG-4 container with MPEG-4 codecs being used for the audio and video.
MPEG-4 is both a container and a codec:
MPEG-4 is a form of MPEG encoding. It
is a flexible audio and video
compression format. The format
describes audio and video compression,
with a container format for streaming
across networks and saving to disk. It
also contains optional extra features,
including DRM and subtitles. These
extra features are only included in
software if needed. MPEG-4 can provide
better quality than MPEG-2 at low
bitrates.
MPEG-4 audio is an advanced, complicated audio format. It includes AAC for high bitrates, multilingual tracks, text-to-speech modes for very low bitrates, the ability to synthesize instrumental sounds (similar to MIDI), and more.
Video:
mp4v
This is a video codec.
This codec can be
used inside the MPEG-4 containers.
This codec is from the ffmpeg module.
Audio:
mp4a
This is an audio codec.
This codec can
be used inside the MPEG-4 containers.
This codec is from the ffmpeg module.
If we were talking about the MP4 container, you could see these types of codecs in them:
Accepted video codecs
mp4v, including
all the codecs described above
mpgv
MJPG
mjpb
SVQ1
SVQ3
H263
h264
Accepted
audio codecs
mp4a (is aac)
mpga
samr
sawb
Accepted subtitle codec
subt
So is mp4a just another name for the aac codec? – jj_ – 2019-02-15T20:37:25.387